In building automation systems, heating, ventilation, and air conditioning (HVAC) installations, pumping systems, and other industrial implementations, it is common to use starters or starter mechanisms to control and protect motors. Starters for motors and the like are generally well known in the art. Typical starters comprise thermal trip elements combined with contactors to disconnect a motor from line power in the event of an undesirable operating condition. The National Electric Code (NEC) classifies combination starters as devices that provide thermal overload protection and motor disconnect functionality.
Key components of a traditional starter include an electromagnetic contactor and an overload relay. The circuitry of such traditional starters offers both motor control and motor protection functionality via a single device that is ideally specifically selected or calibrated for the particular motor being controlled. Operation of the motor (e.g., starting and stopping the motor, etc.) can be controlled through modulation of the contactor, which includes separable contacts that are electromechanically/electromagnetically operated by an energized or de-energized coil. Closing the contacts allows line power to energize the motor, while opening the contacts cuts of power from the motor.
As mentioned above, starters also are able to provide thermal protection (i.e., overload protection) to a motor to protect it against unfavorable operating conditions. Traditional starters typically include an overload relay provided for this purpose. Overload conditions occur when equipment is operated in an electrically undamaged circuit in excess of the normal full load current rating (e.g., the conductors carry current in excess of the rated amperage). The overload is detected by the overload relay with reference to the applicable current trip point (expressed as a trip curve, which designates trip points as a function of current and time for a given motor classification). Overload conditions persisting for a sufficient amount of time can damage the motor, conductors, or other equipment. The terms “overload”, “overload protection” and “overload relay” are defined by the National Electrical Manufacturers Association (NEMA) standard ICS2, which is hereby incorporated by reference in its entirety. In the past, typical overload relays were implemented using heater/detector elements, such as using bimetallic relays or thermal heater elements. More recently, however, electronic overloads have been increasingly used. Electronic overloads may include a current transformer or other current sensor to detect and monitor current supplied to the motor.
For simple electromechanical motors, a traditional starter apparatus with control and overload protection functionality generally provides adequate motor protection if it is property calibrated to the specific motor it is protecting. Each classification of motor has its own applicable overload tollerances and operating parameters. Accordingly, starters that operate motors are required to employ overload relays and corresponding overload trip circuits that are specifically selected and calibrated in order to ensure that the proper level of thermal protection is afforded to the specific motor (or class of motor) being protected. Traditional calibration procedures require an installer to set a trip point manually by dialing one or more potentiometers on an electronic overload relay to a known parameter value, such as the full-load-amperage (“FLA”) rating of the motor, as specified on the motor nameplate and/or on system schematics.
The requirement for properly calibrated protective equipment can pose a problem in situations where several starters are shipped in bulk to an original equipment manufacturer (OEM), and the OEM ships numerous starters in bulk to a job site. Often, the starters arriving at the job site may not be marked or labeled. Installers frequently install the unlabeled starters inappropriately, and then attempt to start attached motors without ensuring proper calibration of the starter. Such procedures are dangerous and can result in damage to equipment, personal injury, or worse. A similar problem can develop if system demands or equipment change, such as when a fan or other equipment is added or ductwork is changed in an HVAC system, or when a motor or pump, etc. is added, removed, or changed out of an installation. Failure to ensure that the starter is, or remains, properly calibrated for the new load it is protecting and/or controlling can result in unintended and/or undesirable consequences.